2.1.5: redox

Question 1

what do oxidation numbers tell us?

Answer 1

how many electrons and atom has donated or accepted to form an ion or compound

Question 2

what is oxidation?

Answer 2

process of losing electrons and involves an increase in oxidation number

Question 3

what is reduction?

Answer 3

process of gaining electrons and involves a decrease in oxidation number

Question 4

how can we remember what oxidation and reduction is?

Answer 4

OILRIG

Question 5

what’s the rule for assigning oxidation numbers to uncombined elements?

Answer 5

they have an oxidation number of 0
e.g. Zn, Cl2, O2
because they haven’t accepted or donated any electrons

Question 6

what’s the rule for assigning oxidation numbers for neutral compounds?

Answer 6

have an overall charge of 0
oxidation numbers of the elements must add up to 0
e.g. NaCl = Na+1, Cl-1

Question 7

what’s the rule for assigning oxidation numbers to monoatomic ion?

Answer 7

equal to the ionic charge

e.g. Cl- = -1

Question 8

what’s the rule for assigning oxidation numbers to polyatomic ions?

Answer 8

the sum of the oxidation numbers of the individual elements must add up to the overall charge of the ion
e.g. CO3 2-
C=+4 O=-2
(3 x -2) + +4 = -2

Question 9

what would the oxidation state of group 1 elements be?

Answer 9

always +1

Question 10

what would the oxidation state of group 2 elements be?

Answer 10

+2

Question 11

what order should you use to work out the oxidation states of any other ions?

Answer 11

Fluorine (F) = -2
Hydrogen (H) = +1
Oxygen (O) = -2
Chlorine (Cl) = -1

Question 12

what is a redox reaction?

Answer 12

where electrons are transferred from one species to another

Question 13

what do you call it when something is reduced and oxidised at the same time?

Answer 13

disproportionation

Question 14

why do we use roman numerals?

Answer 14

to show the oxidation state of the element before it